**Core Concept**
The question is testing the understanding of the mechanism of anticoagulants used in estimating blood glucose levels. **Glucose estimation** in the blood is crucial for diagnosing and managing diabetes mellitus. Certain anticoagulants can interfere with this process by inhibiting glycolysis, the breakdown of glucose to pyruvate.

**Why the Correct Answer is Right**
The correct answer is **Oxalate**. Oxalate is a **bidentate chelating agent** that binds to calcium ions, thus preventing the precipitation of calcium oxalate. This prevents the clotting of blood and allows for accurate estimation of blood glucose levels. **Glycolysis** is the process by which glucose is converted into pyruvate, which is then used to produce energy in the form of ATP. However, oxalate does not directly interfere with glycolysis.

**Why Each Wrong Option is Incorrect**
* **Option A:** Sodium fluoride is an anticoagulant that inhibits glycolysis by preventing the breakdown of glucose to pyruvate. However, it is not the correct answer in this case.
* **Option B:** EDTA (Ethylenediaminetetraacetic acid) is a chelating agent that binds to calcium ions, but it is not typically used as an anticoagulant in glucose estimation.
* **Option C:** No option is provided for this choice.

**Clinical Pearl / High-Yield Fact**
When estimating blood glucose levels, it is essential to use the correct anticoagulant to prevent glycolysis and ensure accurate results. Sodium fluoride is commonly used as an anticoagulant in glucose estimation, as it inhibits glycolysis without interfering with the estimation process.

**Correct Answer:** C.